Using Linq and Trim.Text for Search
I am trying to convert this test code to C # and have a problem with the Trim command. Has anyone done something like this in C # to use this with a search textbox in an aspx page.
Dim q = From b In db.Blogs _
Where b.BlogContents.Contains(txtSearch.Text.Trim()) Or _
b.BlogTitle.Contains(txtSearch.Text.Trim()) _
Select b
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What is the problem? And which LINQ provider is it? In-memory collection (LINQ-to-Objects)? Or LINQ-to-SQL? Or LINQ-to-Entities?
I suspect you are getting something about the LINQ db provider without knowing about Trim () - in that case, try trimming first:
string s = txtSearch.Text.Trim();
var q = from b in db.Blogs
where b.BlogContents.Contains(s) || b.BlogTitle.Contains(s)
select b;
There are two three separate questions in this address :
1: captures: the txtSearch
request is recorded in the source text , which has difficulties; evaluating first Trim
, it is captured s
, which is a simple immutable string
2: Expression Complexity: With LINQ based on expressions (eg in a database), the entire expression (including .Text
, .Trim
etc.) is part of the expression. If the LINQ provider does not recognize one or more of them, it will fail. Bringing it down to a string first, all the LINQ operator has to handle is a string that needs to be fine with every provider.
(added) 3: re-computation: LINQ-to-Objects are very literal; if you ask him to use a complex operation in Where (etc.), it will be, even if it is obvious that the answer does not change in the line; those. txtSearch.Text.Trim()
shouldn't be changed for every line, so why evaluate it per line? Evaluate it before asking and it only gets executed once.
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